Smash the Fat – Calories Part XI

Click here for Calories part I, part II, part III, part IV, part V, part VI, part VII, part VIII, part IX, and part X.


So, here again is our conventional Caloric Reduction model of obesity. It turns out that part of eating too much was entirely hormonally mediated and not personal choice at all (gluttony). It turns out that eating less does NOT cause weight loss, and eating more does not cause weight gain. At least not permanently. For further proof, we turn to the fascinating case of Sam Feltham.


5,000 Calorie Experiment

In a modern twist to the classic overeating experiments, Sam Feltham decided to perform an absolutely fantastic experiment on himself. He would eat 5,000 calories per day of a low carbohydrate, high fat diet (LCHF) consisting of natural, not ‘fake’ foods for 21 days. This is based on the premise that refined carbohydrates and not total calorie count causes weight gain. If that were true, then he would not gain weight despite a very high calorie count because the carbohydrate count was low. Wunderbar!

His diet can be found here. A total of 5,794 calories per day with a macronutrient breakdown of Carbohydrate 10%, Fat 53%, and Protein 37%.

According to standard calorie calculations, he figures that he should have gained 7.3kg of fat (yellow line in graph above). Actual weight gain, however, was 1.3kg.

What is even more interesting (as if that is possible!) is his waist measurements. From a baseline of 79.5cm he dropped 3 cm from his waist which means that even as he gained some weight, much of that is lean mass.

As you can see from the pictures, an excess of calories is simply not sufficient to produce fat gain. Things are far, far, far more nuanced that a simple scale of Calories In vs Calories Out.

There are those who argue that Sam simply has a fast metabolism and no matter what he eats, he will not gain weight. Is that true?

What would happen if Sam were to abandon the LCHF diet? Instead, it would be interesting to see what would happen if he ate 5,000 calories of a standard ‘American Diabetes Association’ style ‘balanced’ diet with a high level of carbohydrate intake.Sam-Feltham-carb-1

What you get is the absolutely brilliant 21-day, 5,000 calorie Carb Challenge. Over 21 days, he would eat 5,793 calories/day of ‘fake’ foods – mostly refined grains and sugars. His diet plan is here. The macronutrient breakdown is 64% carbs, 22% fat, 14% protein. Interestingly this is not too much different than what most nutritional ‘authorities’ recommend for us. So, for the same amount of calories, would he gain or lose weight?


As you can see, his weight gain almost exact mirrors that predicted by the calorie formula – 7.1kg (15.6 lb) weight gain. Waist increased 9.25 cm.

Look at the pictures! Holy double chin, Batman. After only 21 days, the guy is starting to get some love handles, too. This is what you get when you listen to the nutritional ‘authorities’ on obesity.

It is very clear that there is something much more complicated than simple caloric reduction. For the same amount of total caloric increase, one diet – a low carb, high fat, natural foods diet – produced fat loss (waist size decrease).

On the other hand, a standard high carb American Heart Association style diet produced a 15 pound weight gain! So there is something more than calories at work here.


If we abandon the CRaP model and calories entirely, then we can focus on the pertinent question. What causes weight gain? What is the aetiology of obesity? Not calorie counts for sure.

We have seen that the body has a certain body set weight. If you try to go above the weight, the body tries to bring it down. If you try to go below that weight, the body tries to bring it up. So, we can see that the most important question is this: What controls the Body Set Weight?

The only way we can successfully lose weight is to lower the BSW. And we can only do that if we understand what is controlling the body weight ‘thermostat’.

Put it this way. Suppose you set your thermostat in your house to 30C which is very hot and unbearable. In order to cool your house, you now bring in an air conditioner. This cools the house a bit, but then your thermostat turns on the furnace so that the A/C and the furnace are constantly fighting each other.

That is how we currently approach weight loss. We cut calories but we ignore the BSW. You try to lose weight, your body tries to regain the weight. We get hungry and our metabolism starts to shut down.

Wouldn’t it be much, much easier to set the thermostat to 21C – a comfortable temperature, rather than constantly fighting with ourselves? The reason diets are so hard is that we are constantly fighting our own body. So now here is our challenge… we need to figure out “What controls the Body Set Weight?”

That is the next topic we address in the upcoming series “Hormonal Obesity I“.

Begin here with Calories I

Click here to watch the entire lecture: The Aetiology of Obesity – A New Hope

2017-09-02T11:54:32-04:0013 Comments

About the Author:

Dr. Fung is a Toronto based kidney specialist, having graduated from the University of Toronto and finishing his medical specialty at the University of California, Los Angeles in 2001. He is the author of the bestsellers ‘The Obesity Code’ and ‘The Complete Guide to Fasting’. He has pioneered the use of therapeutic fasting for weight loss and type 2 diabetes reversal in his IDM clinic.

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richard meade
richard meade

Still searching for “Hormonal Obesity” series.


The Hormonal Obesity series comes right after the Calories series. I’ve pasted a link to it.


[…] a new book written by a fascinating fellow from the UK by the name of Sam Feltham. I’ve written a previous post about his fascinating self-experiment where he ate over 5,000 calories per day for 21 days. The only […]

Ana Alves
Ana Alves

After eleven posts and we still don´t get the answer??? We need no read more ten posts of another chapter??


Ana, clearly this site is not for you.

I really appreciate the hard work the great doc is doing to make all of this so easy to understand.

Thanks to him. 🙂


I agree with Ana. I don’t get the point of this. If by cutting calories and increasing exercise one cannot successful lose weight and fight obesity. If those “don’t work” then what does work.

The information was interesting but there are no solutions here and it makes me think this information is just (once again) an internet doctor picking and choosing what he wants to say to seem controversial and appealing to the masses.

Vibritality LLC

Ana and Nire,
YouTube Dr. Jason Fung The Aetiology of Obesity and watch the series. You will get reams of information!


And yet: There is no guarantee that every individual would have even similar results to this intriguing young man nor that even a successful regime would lead to the permanent change in habits necessary to sustain the positive body changes, which seems even more important. It doesn’t matter how successful a program is if the majority of those in need find it too difficult to sustain. LC has been around for 150 years. Is there any proof that people are willing to live with it for decades? Is the dietary regime central to long-term adherence, or is it… Read more »

Abe Ramat
Abe Ramat

Doesn’t the American Heart Association diet recommend whole grains? If Sam at a high carb, low fat diets based on whole, unprocessed carbohydrates (not junk food), do you think his results would have been significantly different?


[…] fat? No, no at all. Let’s take the lean person (leptin sensitive) first. Remember the story of Sam Feltham’s 5000 calories/day experiment? He ate an enormous number of calories per day, and still did not gain weight (53% fat, 10% carb). […]

Esmeralda Herrera

I loved what I learned so far …great explanation!! thanks a lot Dr.

Hector Storm
Hector Storm

I can only go from my own experiences, but I don’t believe that 21 days is long enough for this type of experiment. I am an unusually lean individual (BMI around 18, sub-10% BF%), who attempted a similar experiment in 2015, except that I consumed 3,500-4,000 calories a day, not 5,000. I was eating a low-carb, high fat diet, which consisted largely of home made shakes with cream/milk and also nuts. In the first 2-3 weeks, I gained barely 1-2lbs. Between April – October, however, I gained some 25lbs. It was almost unprecedented for me, because I lose weight very… Read more »


Assuming I repeat that experiment and eat a lot more calories than I need (say those 5800 calories on 2 meals a day), what exactly happens if I don’t gain weight (except for muslce buildup)? Where does the energy go? Or more formally, obviously we don’t reduce the fat to CO2 but to something else that has a higher thermic energy. Do we simply produce excess acetate that we exhale? I know that we burn a bit more energy to metabolize fat and protein, and I think Richard Feinman points out that we get a little bit less Acetyl-CoA from… Read more »